Long Term Evolution (LTE) is the latest standard in mobile network technology which is being developed by the 3rd Generation Partnership Project (3GPP). An LTE network architecture consists of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core (EPC). In the E-UTRAN, an evolved NodeB (eNB), as a local radio access point (RAP) or base station (BS), performs all RAN-related functionality. Thus, processing is mostly decentralized at the individual locations of the eNBs.
FIG. 1 illustrates an exemplary LTE network architecture and FIG. 2 illustrates the functions of the E-UTRAN and EPC therein. The eNBs, the only entity of the E-UTRAN, perform all of the RAN functionality including the protocols of layers 1-3 shown in FIG. 3 at their individual decentralized locations. The lowest layer of the protocol stacks, the physical layer (PHY), defines the means of transmission. The Medium Access Control (MAC) sublayer communicates with the physical layers by the transport channels and performs scheduling and multiplexing/demultiplexing functions for transmission between the transport channels and the logical channels which connect to the Radio Link Control (RLC) layer. The RLC protocol is responsible for ordering and adapting the size of data packets being transmitted. Between the layer 2 RLC and the layer 3 Radio Resource Control (RRC) protocol is the Packet Data Convergence Protocol (PDCP), which processes information on the control side with the RRC and in the packets from the user side. To carry out the protocol stack, each eNB is adapted to perform a number of measurement and control functions.
The eNBs communicate with each other via the X2 interface to reduce packet losses which can occur when a mobile user moves from a cell covered by one eNB to a cell covered by another eNB. Accordingly, each eNB is responsible for handling interference between the cells using Radio Resource Management (RRM) functionality. Other functions required of the eNBs include Resource Block (RB) control, connection mobility control, radio admission control and dynamic resource allocation.
The eNBs communicate with the Evolved Packet Core (EPC) via the S1 interface. The EPC includes a Mobility Management Entity (MME), a Serving Gateway (S-GW) and a Packet Data Network Gateway (P-GW). The MME is responsible for authenticating the users, controlling existing sessions therewith and managing incoming sessions. The S-GW serves as a mobility anchor. There is one S-GW for each user device in use at a given time. The P-GW is responsible for IP address allocation for users in the E-UTRAN and filtering of the data packets.